const config = require('../../../config');

// Test if potential opening or closing delimieter
// Assumes that there is a "$" at state.src[pos]
function isValidDelim(state, pos) {
    var prevChar, nextChar,
        max = state.posMax,
        can_open = true,
        can_close = true;

    prevChar = pos > 0 ? state.src.charCodeAt(pos - 1) : -1;
    nextChar = pos + 1 <= max ? state.src.charCodeAt(pos + 1) : -1;

    // Check non-whitespace conditions for opening and closing, and
    // check that closing delimeter isn't followed by a number
    if (prevChar === 0x20/* " " */ || prevChar === 0x09/* \t */ ||
            (nextChar >= 0x30/* "0" */ && nextChar <= 0x39/* "9" */) ||
            nextChar === 0x28 || nextChar === 0xFF08 || // 下一个字符为英文或中文左括号
            prevChar === 0x28 || prevChar === 0xFF08
        ) {
        can_close = false;
    }
    if (nextChar === 0x20/* " " */ || nextChar === 0x09/* \t */ ||
        nextChar === 0x29 || nextChar === 0xFF09 || // 下一个字符为英文或中文右括号
        nextChar === 0x2E || nextChar === 0x3002) {
        can_open = false;
    }

    return {
        can_open: can_open,
        can_close: can_close
    };
}

function math_inline(state, silent) {
    var start, match, token, res, pos, esc_count;

    if (state.src[state.pos] !== "$") { return false; }

    res = isValidDelim(state, state.pos);
    if (!res.can_open) {
        if (!silent) { state.pending += "$"; }
        state.pos += 1;
        return true;
    }

    // First check for and bypass all properly escaped delimieters
    // This loop will assume that the first leading backtick can not
    // be the first character in state.src, which is known since
    // we have found an opening delimieter already.
    start = state.pos + 1;
    match = start;
    while ( (match = state.src.indexOf("$", match)) !== -1) {
        // Found potential $, look for escapes, pos will point to
        // first non escape when complete
        pos = match - 1;
        while (state.src[pos] === "\\") { pos -= 1; }

        // Even number of escapes, potential closing delimiter found
        if ( ((match - pos) % 2) == 1 ) { break; }
        match += 1;
    }

    // No closing delimter found.  Consume $ and continue.
    if (match === -1) {
        if (!silent) { state.pending += "$"; }
        state.pos = start;
        return true;
    }

    // Check if we have empty content, ie: $$.  Do not parse.
    if (match - start === 0) {
        if (!silent) { state.pending += "$$"; }
        state.pos = start + 1;
        return true;
    }

    // Check for valid closing delimiter
    res = isValidDelim(state, match);
    if (!res.can_close) {
        if (!silent) { state.pending += "$"; }
        state.pos = start;
        return true;
    }

    if (!silent) {
        token         = state.push('math_inline', 'math', 0);
        token.markup  = "$";
        token.content = state.src.slice(start, match);
    }

    state.pos = match + 1;
    return true;
}


function math_block(state, startLine, endLine, silent) {
    // 检测起始行是否以 $$ 开头
    const startPos = state.bMarks[startLine] + state.tShift[startLine];
    const endPos = state.eMarks[startLine];
    if (state.src.slice(startPos, startPos + 2) !== '$$') return false;

    let nextLine = startLine;
    let endMarkerLine = -1;
    let endMarkerPos = -1;

    // 从下一行开始寻找结束标记 $$
    for (nextLine = startLine + 1; nextLine < endLine; nextLine++) {
        const lineStart = state.bMarks[nextLine] + state.tShift[nextLine];
        const lineEnd = state.eMarks[nextLine];
        const lineContent = state.src.slice(lineStart, lineEnd);

        // 严格匹配行首的 $$（允许缩进）
        if (lineContent.trim() === '$$') {
            endMarkerLine = nextLine;
            endMarkerPos = lineStart + lineContent.indexOf('$$') + 2;
            break;
        }
    }

    // 未找到闭合标记
    if (endMarkerLine === -1) return false;

    if (silent) return true;

    // 提取公式内容（排除起始行和结束行的 $$）
    const contentStart = startPos + 2;
    const contentEnd = state.bMarks[endMarkerLine] + state.tShift[endMarkerLine];
    const content = state.src.slice(contentStart, contentEnd).trim();

    // 创建公式块 Token
    const token = state.push('math_block', 'math', 0);
    token.content = content;
    token.map = [startLine, endMarkerLine];
    token.markup = '$$';
    token.block = true;

    // 关键！更新解析器到结束行的下一行
    state.line = endMarkerLine + 1;
    return true;
}
// function math_block(state, start, end, silent){
//     var firstLine, lastLine, next, lastPos, found = false, token,
//         pos = state.bMarks[start] + state.tShift[start],
//         max = state.eMarks[start]

//     if(pos + 2 > max){ return false; }
//     if(state.src.slice(pos,pos+2)!=='$$'){ return false; }

//     pos += 2;
//     firstLine = state.src.slice(pos,max);

//     if(silent){ return true; }
//     if(firstLine.trim().slice(-2)==='$$'){
//         // Single line expression
//         firstLine = firstLine.trim().slice(0, -2);
//         found = true;
//     }

//     for(next = start; !found; ){

//         next++;

//         if(next >= end){ break; }

//         pos = state.bMarks[next]+state.tShift[next];
//         max = state.eMarks[next];

//         if(pos < max && state.tShift[next] < state.blkIndent){
//             // non-empty line with negative indent should stop the list:
//             break;
//         }

//         if(state.src.slice(pos,max).trim().slice(-2)==='$$'){
//             lastPos = state.src.slice(0,max).lastIndexOf('$$');
//             lastLine = state.src.slice(pos,lastPos);
//             found = true;
//         }

//     }

//     state.line = next + 1;

//     token = state.push('math_block', 'math', 0);
//     token.block = true;
//     token.content = (firstLine && firstLine.trim() ? firstLine + '\n' : '')
//     + state.getLines(start + 1, next, state.tShift[start], true)
//     + (lastLine && lastLine.trim() ? lastLine : '');
//     token.map = [ start, state.line ];
//     token.markup = '$$';
//     return true;
// }

module.exports = md => {
    var inlineRenderer = function(tokens, idx){
      return `<latex value="${encodeURIComponent(tokens[idx].content).replace(/'/g,'%27')}" type="line"></latex>`;
    };

    var blockRenderer = function(tokens, idx){
      return `<latex value="${encodeURIComponent(tokens[idx].content).replace(/'/g, '%27')}" type="block"></latex>`;
    };

    md.inline.ruler.after('escape', 'math_inline', math_inline);
    md.block.ruler.after('blockquote', 'math_block', math_block, {
        alt: [ 'paragraph', 'reference', 'blockquote', 'list' ]
    });
    md.renderer.rules.math_inline = inlineRenderer;
    md.renderer.rules.math_block = blockRenderer;
};